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COAL EXPLORATION AND EXPLOITATION

Stages

The stages in the development of a coal mine may spread over 10 years :-

Stage 1  Stage 2  Stage 3  Stage 4  Stage 5  Stage 6       Potential Preliminary Intensive Feasibility Planning Development prospects exploration exploration study

Exploration work involves - drawing detailed geological maps - sinking boreholes to obtain rock samples - analysis of rock samples - prediction of the future yield of the coalfield. (taking into account geological features eg. seam splitting, thickness, faults, dip etc.)

Feasibility studies involve - determining mining engineering costs - identifying environmental impacts - assessing economic viability of mine

Exploitation in Britain

Points to remember :- 1. Easiest workings on exposed coalfields have been exhausted. 2. Improved technology has made it possible to mine deeper and with fewer people. 3. Large reserves are available 4. Restrictions on production at present are social and economic rather than geological.

Mining methods:

1. Open cast mining

 12% of UK coal production - economic down to 200m depth (the most important economic factor is the ratio of overburden to coal - 15:1 for bituminous coal, 20:1 for anthracite)  soil and rock (overburden) stripped away, coal seam broken up then coal removed by drag-line excavators  advantages - mine brought into production quickly - quicker method of extraction - cheaper (fewer people, no expensive tunnels, lifts or pumps) - quicker (machines used) - safer (no rock falls, explosions, flooding) -land can be restored to original use at end

2. Underground mining

 economic down to 1200m  most mines highly mechanized

 deep mining  vertical shaft & galleries/ tunnels leading off, ventilation shafts needed  drift mining  two parallel tunnels (drifts) cut along a slope. Drift tunnels off the main system used to work the coal, ventilation shafts needed.  coal cut away by shearers which work along faces about 200m long (longwall mining). Lines of powered roof supports move forward to hold up the new roof, the area behind the supports is then allowed to collapse.

Question

Study the sketch below. a) Suggest two advantages of the baffle bank during mining. b) What would the baffle bank be built of? c) What could you do after mining finishes here?

Baffle bank

Village

Open cast mine